1. Field of the Invention
The present invention relates to an object detecting device for detecting an object in a target area, based on a state of reflected light when light is projected onto the target area, and an information acquiring device incorporated with the object detecting device.
2. Disclosure of Related Art
Conventionally, there has been developed an object detecting device using light in various fields. An object detecting device incorporated with a so-called distance image sensor is operable to detect not only a two-dimensional image on a two-dimensional plane but also a depthwise shape or a movement of an object to be detected. In such an object detecting device, light in a predetermined wavelength band is projected from a laser light source or an LED (Light Emitting Diode) onto a target area, and light reflected on the target area is received by a light receiving element such as a CMOS image sensor. Various types of sensors are known as the distance image sensor.
A distance image sensor configured to scan a target area with laser light having a predetermined dot pattern is operable to receive a dot pattern reflected on the target area on an image sensor for detecting a distance to each portion of an object to be detected, based on a light receiving position of the dot pattern on the image sensor, using a triangulation method (see e.g. pp. 1279-1280, the 19th Annual Conference Proceedings (Sep. 18-20, 2001) by the Robotics Society of Japan).
In the above method, for instance, laser light having a dot pattern is emitted in a state that a reflection plane is disposed at a position away from an irradiation portion of laser light by a certain distance, and the dot pattern of laser light irradiated onto the image sensor is retained as a template. Then, a matching operation is performed between a dot pattern of laser light irradiated onto the image sensor at the time of actual measurement, and the dot pattern retained in the template for detecting to which position on the dot pattern at the time of actual measurement, a segment area set on the dot pattern of the template has moved. The distance to each portion, in the target area, corresponding to each segment area, is calculated, based on the moving amount.
In the object detecting device thus constructed, at the time of actual measurement, a dot of laser light may be irradiated onto the image sensor in a state that the dot overlaps a plurality of pixels on the image sensor. In such a case, signals may be concurrently outputted from the pixels adjacent to each other, onto which the dot has been concurrently irradiated. As a result, in a dot pattern to be obtained based on an output from the image sensor, some borderlines between dots may not be discriminated as a whole. Thus, it may be impossible to perform a matching operation between a dot pattern of laser light irradiated onto the image sensor at the time of actual measurement, and the dot pattern retained in the template. As a result, detection precision of a distance to each portion of an object to be detected may be lowered.